Technical Field of the Disclosure
The present teachings relate to devices and methods for producing a consistently high density material having a desired length and size.
Description of the Related Art
In the field of food and feed processing, grain densifying and die systems are used to produce high quality densified grain for industrial purpose and animal consumption. In general, it has been recognized that construction of the die apparatus, also commonly known as a pellet mill or extruder die, is a critical factor in obtaining desirable pellets as well as high production rates. For example, the thickness of the die, the number of holes in the die, and the surface finish of the die have all been found to affect pellet quality.
In a typical extrusion die apparatus, it is adapted for coupling to the outlet end of an extruder barrel. In operation, the die apparatus is fed the product from the extruder barrel and shapes the product into a final extrudate, which is cut by a rotating knife to form pellets having predetermined lengths.
However, some existing processes fail to remove all the moisture or air or both from the final pellet, which subjects the pellets to increased decomposition and breakdown during normal handling, storage, and transport. This decreases the percentage of useful pellets.
In conventional pelleting techniques or extrusion techniques, steam is required to be added to the raw material during product densification. While steam is being added to the raw material, air is also continuously introduced into the raw material causing the material to contain substantially more air and water, which adversely affects the ultimate density. The more air and water contained in the material, the less dense the final product becomes after exiting the die. This is due to the fact that the water is not compressible, whereas air is compressible. Therefore, when the final product is subjected to vibrations and jostling, for example, associated with vehicular transport or transport to an accumulation bin, the product may begin to crumble, split or break apart at sites along weak points where the water and air are mixed within the product. These breaking points in the products create fines, which are the materials that result from products, such as pellets, disintegrating, due to poor quality. Fines can be a function of moisture and high friction or oversized feed ingredient particles. Fines are one of the major factors in determining consumer satisfaction with feed quality. To achieve a sufficiently consistent product with this conventional process, it requires more energy to obtain the desired pellet output.
Furthermore, when large diameter or oversized products are produced, they will become even hotter when the raw material mixed with the steam and air is pushed into the final die for forming the shape of the final product. This increased heat causes the water in the product to vaporize into the form of steam which breaks apart the product back to a loose form. One method to mitigate the breaking up of such oversized products is reducing the throughput of raw material through the die, which diminishes the output.
Another method to combat this problem of moisture and air entrapped in the raw material is to add binders, or fillers or both that allow the pellet to bind in a dense form in high heat. The problem with this method is that it drastically reduces the nutritional value of the final product by as much as 60%. The pellet quality can be seriously affected with the addition of too much binder. Lowering the nutritional value increases the cost and negatively affects the final product as a nutritional feed product. The farmer has to feed twice as much tonnage to his animals on a daily basis, which is very costly.
Therefore, there is a need for a method and apparatus for generating pellets with sufficient density for effective transportation, handling and storage practices, without the need for adding additional binders or fillers or both. There is also a need for a method and apparatus that eliminates fines produced in feed products. There is a further need for a method and apparatus that does not require the reduction in throughput of the process to eliminate fines which is the product breaking up during storage or transport.